Heretofore, it has been common to apply surface coating such as coating with a synthetic resin coating material to articles such as metals, inorganic materials, plastics, wood materials, papers, leathers or fibers to form a hydrophobic synthetic resin coating film on their surface for the purposes of their protection, imparting an artistic effect, imparting a functional property, etc.
Recently, as a coating material excellent in weather resistance, a fluoropolymer coating material is used in many cases. Such a fluoropolymer coating material shows a remarkably high weather resistance as compared with prior synthetic resin coating materials. However, soils deposited on its surface are of the same level as in the case of other synthetic resin coating materials, and an improvement in this respect is desired as a high performance commercial product.
Especially, with an article having a hydrophobic synthetic resin coating film, which is used outdoor (hereinafter referred to as an outdoor article), spot-like soils due to rain water are likely to form on the hydrophobic synthetic resin coating film surface exposed to rain. Further, streak-like soils (hereinafter referred to as rain streak soils) are likely to form at a portion where rain water collects and runs down, such as below a window frame of a building. Such rain streak soils can easily be removed by cleaning. However, not only repeated cleaning is cumbersome, but also the cleaning operation is not easy in the case of a large size outdoor article such as a building. Accordingly, a coated outdoor article is desired which has a surface less susceptible to formation of rain streak soils.
Heretofore, to solve the formation of the soils on the surface of a coated article, a composition for a coating material has been proposed wherein a polymer having a polyfluorinated carbon chain and a hydrophilic group, is incorporated (Japanese Unexamined Patent Publication No. 198653/1989). However, the coating surface obtained by this composition for a coating material was not adequate with respect to the point of preventing formation of rain streak soils, although some effects for suppressing formation of spot-like soils due to rain water are observed.
The present inventors have found a surface treating agent which is effective particularly for preventing formation of rain streak soils on the surface of an outdoor article having a hydrophobic synthetic resin coating film surface. The present invention provides a method for treating the surface of the above mentioned outdoor article by means of such a surface treating agent and an outdoor article having the surface treated by such a method.